Manufacture of aliphatic amines



Pnenea M26, 1944 MANUFACTURE ALIPHATIC AMINES John Frank Olin, Grosse IleQand James Francis McKenna, Wyan'dottc, Mich., aaslgnors to Sharples Chemicals Inc., Philadelphia, Pa., a

corporation of Delaware No Drawing. Application October 31, 1941,

Serial No. 417,272

'8 Claims.

The present invention pertains to the manufacture of aliphatic amines by alkylation of ammonia in the vapor phase with primary and secondary open chain alcohols containing between 2 and 8 carbon atoms, Reactions of this type have been known since the initial research work done by Sabatier and Mailhe on use of dehydrating catalysts in this reaction, which was reported in Comptes Rendus, volume 148, page 898 (1909).

In an article at volume 8a, pages241 to 246 of the Memoirs of the College of Kioto, Japan (1925), Hara and Komatsu discuss condensation of amines with alcohols in the presence of metallic hydrogenation catalysts. Thus, by conducting this reaction in the vapor phase at a temperature of 300 C. over a copper catalyst, Hara and Komatsu obtained a reaction product consisting principally of nitrile and aldehyde, but containing also from a trace to 4.2% of amines (page 243). While the work discussed in this paper pertains principally to the development of a new synthesis of nitriles, it is interesting to note that Hara and Komatsu determined that a small amount of basic reaction products were also obtained in the practice of their process.

A second disclosure which is of interest with respect tothis problem is that contained in the U. S. patent to Ernst et al., 1,982,985, and the corresponding British patents, 306,414 and 334,579. These patent disclosures are concerned primarily with the manufacture of cycloaliphatic amines by simultaneous hydrogenation and amination of phenols. In order to accomplish this combined result, Ernst et a1. pass the phenols, together with hydrogen and ammonia, over a, hydrogenation catalyst Ernst et al. also proposed to manufacture aliphatic amines by passage of an alcohol and ammonia over a hydrogenation catalyst, but in this connection they omitted the use of hydrogen, the only function of hydrogen in any part of their process being apparently one of hydrogenating aromatic compounds to produce corresponding cycle-aliphatic compounds or preventing dehydrogenation of cycloaliphatic compounds by mass action eii'ect. Ernst et a1. recommended a temperature of 300 C. in manufacture of butyl amine, and, as pointed out above, they omit the use of hydrogen in cases in which aliphatic alco- From the results obtained by Hara, and Komatsu, it is quite evident that, while such a process may produce a small amount of amines, as indicated by the results obtained by Hara and Komatsu, neither the yields nor conversions are such as to compare at all favorably with the already known process of Sabatier involving use of dehydration hols are condensed with ammonia. A similar of a process for manufacturing aliphatic amines is concerned, is identical with the process taught by Kara and Komatsu for manufacture of nitriles.

catalysts. Research by the present applicants and others has indicated that Hara and Komatsu were entirely right in determining that his process, while it produced nitriles, was an entirely inadequate solution to the problem of producing amines in substantial yields.

A defect of the Ernst et al. patent as well as of French Patent 687,393 consists in the fact that, if an aliphatic amine is the desired resultant of the reaction, this aliphatic amine is obtained only in very inferior yield, due to the formation of nitrile in the practice of the reaction. In experiments conducted by the present applicants involving passage of butyl alcohol and ammonia over a nickel catalyst at temperatures between and 0., a reaction product was obtained which contained only 34% of butyl amines, most of the remainder of the product consisting of butyronitrile. A further defect of the process, as practiced under these conditions, consisted in the fact that the rate of conversion of the alcohol to nitrogen compounds was relatively slow. with the result that the process was ineiiicient from this point of view.

The observations made above with respect-to prior art suggestions of use of hydrogenation catalysts in this reaction are substantially in line with those of the U. S. patent to Guinot, 2,053,193. Guinot, like the present applicants, examined the prior art relative to this process, but could find inthat prior art nothing which could be regarded as an improvement over the Sabatier process. Guinot proposed a solution to the problem involving initial performance of a stepsimilar to that performed by Hara and Komatsu, involving deliberate conversion of the reactants to nitrile, followed by hydrogenation of the nitrile at relatively low temperatures to produce the desired amine.

The applicants have discovered that a hydrogenation catalyst may be used in manufacture of amines from primary and secondary open chain alcohols containing between 2 and 8 carbon atoms, with yields and conversions superior to any-heretofore obtained in the use of dehydration catalysts or any other catalysts, provided the reaction is conducted at temperatures between 150 and 230 ,C. in the presence of metallic hydrogenation catalysts, such as nickel or cobalt, and provided further t at a substantial quantity of hydrogen be incorpfirated in the reaction mixture. By the simple expedient of conducting the alcohol together with ammonia and hydrogen at these relatively low temperatures over the hydrogenation catalysts, the applicants have provided a process which'is incomparably superior to the Ernst process or the process of French Patent 687,398. They have found that it is entirely unnecessary to resort to the elaborate procedure of Guinot to avoid the difliculties of these prior patents, provided the temperature is kept within the relatively narrow range indicated above, and a substantial quantity of hydrogen is also maintained in the reaction mixture during its contact with the hydrogenation catalyst. By the practice of this process, they have been able to convert secondary alcohols as well as primary alcohols into the desired amines in excellent yields and conversions, a result never heretofore achieved, inscfar as they are aware.

The invention will be better understood from the following detailed discussion of the best conditions for the performance thereof.

In the preferred practice of the invention, the aliphatic alcohol which is to serve as the alkylating agent is first mixed with ammonia in the proportions adapted to produce the desired mixture of mono-, di-, and tri-alkyl amines, and a quantity of hydrogen, which is preferably at least a molecular equivalent of the alcohol under treatment, is also incorporated in the reaction mixture. In this connection, it is pointed out that any amount of hydrogen whatever, when incorporated in the mixture, will improve the results in the amination reaction as compared to prior art processes, but in order to produce best results, it is desirable that at least one mole of hydrogen for each mole of alcohol be provided. The very best results in the practice of the invention are attained when the hydrogen is present in a considerable molecularexcess, and we recommend that at least a 4:1 molar ratio of hydrogen to alcohol be used.

It is desirable that the alcohol, ammonia and hydrogen be thoroughly mixed before being passed in vapor phase through the chamber containing the metallic hydrogenation catalyst. It is also desirable that the reaction mixture be preheated to approximately the reaction temperature (i. e.'. between 150 and 230 C.) before being passed across the catalyst to accomplish the alkylation of the ammonia.

The ratio between the mono-, di-, and trialkyl amine reaction roducts produced in the practice of the inverLion will, of course, depend upon the ratio of ammonia to alcohol employed in the reaction. Best results as to yields and conversions have been attained. in cases in which this molecular ratio includes between 2 and 5.5 moles of ammonia for each mole of alcohol in the mixture. In any case, it is desirable that the ammonia be present in a molecular excess over the alcohol, since the result of employing less than a molecular equivalent of ammonia would be to destroy a part of the alcohol by undesired hydrogenolysis.

Summarizing and illustrating the above discussion, in the preferred practice of the process of the invention, vapor phase streams of alcohol, ammonia and hydrogen may be passed into confiuence in the ratio of 1 mole of alcohol to between 2 and 5.5 moles of ammonia and between 4. and 6 moles of hydrogen. These gases are thoroughly mixed and then travel together through a pre-heater which heats them to the desired temperature (e. g., 190 C.) before they pass on to the reactor. The temperature of the .mixture as it enters the reactor will depend somewhat upon the space velocity and other conditions, as to be discussed hereinafter. The mixture is then passed through the reactor containing the hydrogenation catalyst, which is preferably reduced nickel, but may be some other metallic hydrogenation catalyst, such as cobalt. After passage across the hydrogenation catalyst and formation of the desired amine reaction mixture, the constituents of the mixture which are less volatile than ammonia may be condensed and separated from' the ammonia and hydrogen. The volatile products (principally ammonia and' hydrogen) through an activated charcoal adsorber which removes any less volatile reaction products contained therein, together with a part of the ammonia. The remaining ammonia and hydrogen may then be recirculated through the system by mixing them with a further quantity of the alcohol in the desired proportion.

The invention may be practiced at pressures varying anywhere from atmospheric pressure to pressures in excess of 500 lbs. per square inch. One feature of the invention consists, however, in

the use of pressures in excess of 40 pounds per,

square inch in practice of the invention, since, although the use of these pressures slightly retards the progress of the reaction in the desired direction, it decreases the formation of undesired nitriles and hydrocarbons.

While the invention may be carried out at various temperatures within the range between 150 and 230 0., best results have been attained within a narrower range between 180 and 210 40 C., in cases in which a nickel catalyst 'was used and the space velocity adjusted to attain a fairly high rate of passage of the reactants through the apparatus. The particular temperature employed is, of course, largely dependent upon the space velocity through the catalyst" bed, a higher temperature being necessary to obtain high conversions in cases in which a high space velocity is employed than in cases in which a lower space velocity is employed. Thus, in manufacture of butyl amine, an 87% conversion of the alcohol to amine may be attained at a space velocity of about 2100 and a temperature of C., but the space velocity may be stepped up to 3500 with a similar conversion in case the temperature is increased to 195 C. In cases in which the space velocity is between 3000 and 4000 in the manufacture of ethyl amine, best results as to conversion are obtained if the catalyst chamber is maintained at a temperature between and C. If the temperature is maintained below this range, the rate of conversion decreases rapidly, with the result that the space velocity must be decreased in order to attain a comparable conversion in a single pass of the reactants through the apparatus; if, on the other hand, the temperature is raised, the yield will be somewhat impaired by conversion of the alcohol molecule to hydrocarbon.

The practice of the process of the invention will result in formation of mixtures of the three amines corresponding to the alcohol used, regardless of the exact proportion of the reactants, but the ratio between the three resultant amines may be controlled by proper control of the ratio of alcohol to ammonia. A further control of the may then be passed The following examples illustrate the practice -of the invention:

Example I During a period of hours, 5.2 moles of ethanol mixed with 46.1 moles of hydrogen and 29.6 moles of ammonia was passed through 175 cc. of 'a reduced pelleted nickel hydrogenation catalyst maintained at an average temperature of 159 C. and a space velocity of 2070. The ammonia free reaction mixture (weight 312 grams) was worked up by an acidification technique which consisted in the removal of the monoethylamine, acidification of the remaining amines and removal by distillation of the unreacted ethanol and other volatile neutral materials. Then by adding caustic in excess to the cooled acidic resi- {due nd distilling, the diethylamine and triethylamine were obtained. In this manner there was 'aobtained 60.2 grams of ethylamine for a 25.8%

,iconversion and 27.4% yield, 80.5 grams of diethylamine for a conversion and yield of 42.4%

and 45.0% respectively and 21.3 grams of triethylamine for a 12.1% conversion and a 12.8%

yield.

Example II 171 lbs. of ethanol (28 gallons of a specially denatured alcohol containing 5% of mixed ethylamines), 47.25 lbs. of ammonia and 35.0 cu. ft. of hydrogen were reacted in the presence of 1.2 cu. ft. of a pelleted nickel hydrogenation catalyst during a period of 4 hours. The fixed gases, hydrogen and ammonia, were recirculated at such a rate that the ratio of ethanol to ammonia to hydrogen was kept at 1:25:49, and a space velocity of 2460 was maintained. Tile reactants entered the reactor under a pressure of 57.4 lbs. per sq. in. and at an average temperature of 185.2 C. while the average temperature of the reaction mixture was 180.0 C. An analysis of the crude product revealed the presence of 16.5 lbs. of monoethylamine, 53.1 lbs. of diethylamine, 26.9

ethylamine, diethylainine, and trlethylamine were 20.1%, 37.2% and 10.9%, respectively and the yields were 29.4%, 54.5% and 16.0%, respectively.

Example IV During a period of 42 hours 61.1 moles of butanol (4520 grams), 370 moles of ammonia (6290 grams) and 397 moles of hydrogen (794 grams) were passed through 194 cc. of a pelleted nickel hydrogenation catalyst at an average temperature of 181 C. and with a space velocity 01 r 2250. The product was worked up by a direct distillation of the monobutylamine fraction to a temperature of about C., whereupon a decanter was introduced into the systemand dis tillation continued, removing water and some butanol until the residual product was anhydrous. The monobutylamine fraction was redistilled to yield 1083 grams of butylamine. Upon continuing the distillation of the dehydrated product 1836 grams of dibutylamine, boiling between 158 and C. was obtained together with 571 grams of tributylamine boiling between 210 and 218 C. Upon distilling the water which had been removed during the dehydration operation ther was isolated 273 grams of butanol. The latter product was found to be of good purity, boiling over a narrow range and containing only 2.4% of butyronitrile. Summarizing the resultstherewas obtained a 24.4% conversion to monobutylamine, a 46.7% conversion to dib ylamine and a 15.2% conversion to tributylamine. The total conversion of butanol to amines was thereiore 86.3%, and taking into account the recovered butanol the yield was in excess of 91.6%.

CompamtifiEYztnpZe V (conducted the absencggjltydrogen) 5.44 moles of butanol and moles of am monia were conducted in a period of 5 hours lbs. of triethylamine, 0.3 lbs. of acetonitrile and a Example III 152.5 lbs. of ethanol (25 gal. of a special denatured alcohol containing 5% mixed ethylamines) and 31.75 lbs. of ammonia were reacted in the amine pilot plant under a pressure of 197.25 lbs. per sq. in. in the presence of. 107.5 cu. ft. of hydrogen and 1.2 cu. ft. of a pelleted nickel on 'eselguhr hydrogenation catalyst. The reacnts reached the catalyst at atemperature of 193 C. while the catalyst bed was maintained at an average temperature of 194.3 C. The gases were recirculated so that a spacevelocity of 3650 and ratios of ethanol to ammonia to hydrogen of 1:3.0:5.3 were maintained. The crude product was found to contain 30.0 lbs. of monoethylamine, 45.0 lbs. of diethylamine and 12.2'lbs. of triethylamine, with 0.2 lbs. of acetonitrile ,and 50.9 lbs. of ethanol. The conversion to monothrough 194 cc. of pelleted nickel hydrogenation catalyst maintained at a temperature of 181 C. In this reaction 35.2 moles of nitrogen was used as a sweeping gas to keep the space velocity close to that of the comparable reaction where hydrogen was used. The space velocity of this reaction was calculated to be 1630. The ammonia free product (442.7 grams) was worked up by an acidification technique in which the product was acidified by addition of 50% sulfuric acid followed by a distillation to remove the neutral materials contained in the reaction crude. This neutral material was dried by an azeotropic distillation to leave 220.0 grams of anhydrous material with a specific gravity of 0.796 at 33 C.

A Kjeldahl analysis revealed the presence of 45% of butyronitrile. The residue from the reaction crude was neutralized by the addition of an excess of caustic. This was further distilled to yield 89.8 grams of mono-butylamine for a 21.7% conversion, 45.6 grams of dibutylamine for an 11.8% conversion, and a trace of tributylamine. From this experiment the necessity of hydrogen is readily seen.

Example VI In a period of 4 /2 hours 229 lbs. of butanol and 64.5 lbs. of ammonia were reacted by passage through 1.2 cu. ft. of pelleted nickel hydrogenation catalyst at an average temperature of 195 C. While no hydrogen was added from an external source the fixed gases were recirculated so rapidly that the hydrogen concentration built up rapidly, and thus the average molar ratio of butanol to ammonia to hydrogen was found by analysis to be 1:6.4:8.'7. The reactants entered the reactor at a temperature of 198 C. while the system was maintained at a pressure of 16 lbs. per sq. in. and the space velocity was calculated to be 3330. An analysis of the product revealed conversions and yields as follows: butylamine 36.8% conversion and 39.0% yield, dibutylamine 43.3% conversion and 46.0% yield, tributylamine 8.2% conversion and 8.7% yield, butyronitrile 2.6% conversion and 2.8% yield,

butanol recovered 5.7%.

Example VII 1 6.7 moles of diethylcarbinol (590grams), 58.1 moles of ammonia (988 grams) and 34.3 moles of hydrogen were passed over an activated pelleted nickel on silica hydrogenation catalyst at an average temperature of 190 C. and a space velocity of 2340. After removal of the ammonia from the product it was worked up by an acidification and distillation process to remove the nonbasic materials. In this manner 140 grams of diethylcarbinol and diethyl ketone, corresponding to 23.6% of the alcohol charged were recovered. After making the product alkaline with an excess of sodium hydroxide there was obtained 432 grams of 3-aminopentane, corresponding to a 65% conversion, and 30. grams of di-sec-amylamine, corresponding to a 5.6% conversion. It should be stated that the amount of diethyl ketone in the recovered diethylcarbinol is relatively small and may be recycled in the next operation without deleterious effect.

.Monoand di-alkyl amines may be substituted for ammonia in the reaction, as illustrated by the following example.

Example VIII 10.5 moles of ethylamine, 5.2 moles of butanol and 38.3 moles of hydrogen were passed through a pelleted nickel hydrogenation catalyst at an average temperature of 150 C. and a space velocity of 1380. The product was worked up by the acidification technique and was found to provide a 24.8% conversion to N-ethyl butylamine and a 14.8% conversion to N-ethyl dibutylamine. In addition, minor quantities of diethylamine, dibutylamine, butylamine, and N-butyl diethylamine were noted to have been formed in the reaction. The yield of all products, based upon material charged, was excellent.

Modifications will be obvious to those skilled in the art, and we do not therefore wish to be limited except by the scope of the following claims.

We claim:

tinuously chosen from kins.

more than eight "tarball" was. witl ilaiinmonia which comprises passinganiixture of said alco hol, together with ammtmaanq hydrogen, con- 1. The method of making aliphatic amines by condensing an alcohol chosen from the class consisting of open chain primary and secondary all tinuously over anietanic nickel liydrogen'ation catalyst ata temperature betwetmisq'anazso o. f

4. The method?Of -makingaliphatid amihes by condensing analcohol"clic'isenfromthe class con sisting of openchain primary and-secondary'alfi phatic alcohols containing at least two and notmore than eight carbon atoms with ammonia, which comprises passing a mixture of said 'alco hol, together with 'ammoni'aand hydrogen, con-' tinuously overa metallic nickel hydrogenation catalyst at a temperature between '180 and 210 C. 5. The method of making aliphatic amines by condensing an alcohol chosen from the class consisting of open chain primary and secondary all phatic alcohols containing at least two andnot more than eight carbon atoms with ammonia, which comprises passing a mixture of said alcohol, togethefwith ammonia and a quantity of hydrogen bearing, a molecular-ratio to the alcohol under treatment or'at least 1:"1, continuously over a metallic hydrogenation catalyst at a temperature between and 230 C.

6. The methodof making aliphatic amines by condensing an alcohol chosen from the classcon-.

sisting of open chain primary and secondary. aliphatic alcohols containing at least two and not more than eight carbon atoms with ammonia. which comprises passing a mixture of 'said alcohol, together with.am monia"and a quantity of hydrogen bearing a molecular ratio to the alcohol under treatment of at least 4:1, continuously over a metallic hydrogenation catalyst at a temperature between 150 and 230 C.

7. The method of making aliphatic amines by condensing an alcohol chosen from the class consisting of open chain primary and secondary aliphatic alcohols containing at least two and not more than eight carbon atoms with ammonia, which comprises passing a mixture of said alcohol, together with ammonia and a quantity of hydrogen bearing a molecular ratio to the alcohol under treatment of at least 4:1, continuously over a metallic nickel hydrogenation catalyst at a temperature between 150 and 230 C.

8. The method of making ethyl amines by condensing ethyl alcohol with ammonia, which comprises passing a mixture ll ethyl alcohol, ammonia, and an amount u; avdrogen constituting at least a 4:1 molecular 1" 1 to the alcohol under treatment continuously wer a metallic hydrogenation catalyst at a temperature between 180 and 210 C.

JOHN FRANK OLIN. JAMES FRANCIS MCKENNA.

phatic alcohols ;.containingat.leastjtw .a'nd ',not' 

